Small interfering RNAs (siRNAs) can be used to suppress gene expression in a wide variety of organisms, the discovery of which has led to several strategies of triggering RNA interference for therapeutic purposes. Success of therapeutic siRNAs, as editor Sioud (immunology, the Norwegian Radium Hospital, U. of Oslo, Norway) observes in his preface, will depend on developing delivery vehicles that can target pathogenic cell and on increased understanding of the biogenesis of microRNAs (miRNAs). He presents 22 chapters reviewing advances in siRNA design, expression, delivery, and in vivo imaging, as well as methods to minimize siRNA unwanted effects and use in patients. Contributions discuss current tools for siRNA design; the elimination of siRNA unwanted effects, including the activation of innate immunity and off-target effects; approaches to in vivo delivery of siRNAs using nanoparticles, new lipid formations, and receptor-mediated targeting; development of nuclease-resistant siRNAs for a new class of therapeutic drug; the expression of synthetic siRNA/miRNA from a synthetic stem-loop precursor based on miRNA 155 and miRNA 30 precursors; therapeutic target genes, both in vitro and in vivo; miRNA expression, function, and involvement in disease; and the first clinical trial involving a leukemia patient using a synthetic siRNA against Bcl- Abl fusion transcript. Annotation ©2009 Book News, Inc., Portland, OR (booknews.com)